PAGE   60,132

;  CLR.ASM   05/29/84

;  Subroutine called by a basic program to scroll a window.

;

;

DGROUP	GROUP	DATASEG

DATASEG SEGMENT PARA PUBLIC 'DATA'

FUNCT	DW	0		;function 1=6,0=7

FG_COLR DW	0		;forground color

BG_COLR DW	0		;backround color

LINES	DW	0		;number of lines to scroll or 0 for clear

ULROW	DW	0		;upper left row

ULCOL	DW	0		;upper left column

LRROW	DW	0		;lower right row

LRCOL	DW	0		;lower left column

ATTRIB	DB	0		;temp hold for attribute byte

CALNU	DB	0		;temp hold for call function 6 or 7

DATASEG ENDS

;

CSEG	SEGMENT 'CODE'

	ASSUME	CS:CSEG

	PUBLIC CLR

CLR	PROC	FAR

	PUSH	BP		;BP unknown (don't care)

	MOV	BP,SP		;set base for parm list

	PUSH	DS		;DS -> basic work area

	PUSH	ES		;ES -> basic work area

	MOV	AX,DATASEG	;establish data addressability

	MOV	DS,AX		;now DS -> my data

	ASSUME	DS:DATASEG

;

;

	MOV	SI,SS:[BP 6]   ;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	FUNCT,AX

	MOV	SI,SS:[BP 8]   ;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	BG_COLR,AX

	MOV	SI,SS:[BP 10]	;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	FG_COLR,AX

	MOV	SI,SS:[BP 12]	;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	LINES,AX

	MOV	SI,SS:[BP 14]	;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	ULROW,AX

	MOV	SI,SS:[BP 16]	;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	ULCOL,AX

	MOV	SI,SS:[BP 18]	 ;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	LRROW,AX

	MOV	SI,SS:[BP 20]	 ;get addr of parameter

	MOV	AX,ES:[SI]	;get value of parm

	MOV	LRCOL,AX

;

	MOV	AX,1

	SUB	LRROW,AX	;convert 1-80 cols

	SUB	LRCOL,AX	; and 1-25 rows into

	SUB	ULROW,AX	; 0-79 cols and

	SUB	ULCOL,AX	; 0-24 rows

;

;  change forground & backround colors into single attribute byte

;

	MOV	BX,FG_COLR	;move foreground color to bx

	MOV	AL,BL		;move lower byte to al

	MOV	BX,BG_COLR	;move backround color to bx

	MOV	AH,BL		;move lower byte to ah

	CMP	AL,15		;check for color > 15 ie blinking

	JG	BLNK		;if > 15 then set blink bit

	AND	AL,15		;set normal fg color

	JMP	N_BLNK		;

BLNK:	OR	AL,128		;set blink bit 7

	AND	AL,143		;zero out bit 6,5,4 used for backround

N_BLNK: AND	AH,7		;zero out bit 7,6,5,4,3 used for forground

	MOV	CL,4		;4 bit shift count

	SHL	AH,CL		;shift right 3 bits to pos 6,5,4

	OR	AL,AH		;combine for & back to form attribute byte

	MOV	ATTRIB,AL	;move it to STORAGE



;

;   convert 1 and 0 to 6 and 7 for routine call

;

	MOV	BX,FUNCT	;move function into bx

	CMP	BL,0		;compare to one

	JG	F6		;if 1 then function is 6

	MOV	AH,7H		;set function 7

	JMP	OUT1		;jump around

F6:	MOV	AH,6H		;set function 6

OUT1:	MOV	CALNU,AH	;move it to storage

;

;

;  set up for bios rom call 10 function 6 (scroll up )

;

	PUSH	BX

	MOV	BX,LINES	;set # of lines to scroll or 0 to clear

	MOV	AL,BL		;put in pass register

	MOV	BX,ULROW	;set upper left row of block 0-24

	MOV	CH,BL		;put in pass register

	MOV	BX,ULCOL	;set upper left column of block 0-79

	MOV	CL,BL		;put in pass register

	MOV	BX,LRROW	;set lower right row of block 0-24

	MOV	DH,BL		;put in pass register

	MOV	BX,LRCOL	;set lower right column of block 0-79

	MOV	DL,BL		;put in pass register

	MOV	BL,CALNU	;set call number 6 to scroll up 7 down

	MOV	AH,BL		;put in pass register

	MOV	BL,ATTRIB	;set color attribute byte

	MOV	BH,BL		;put in pass register

	INT	10H		; make bios call

	POP	BX

;

FINISH: POP	ES

	POP	DS

	POP	BP

	RET	16		;return to basic

CLR	ENDP

CSEG	ENDS

	END